This invention relates to a cooling apparatus equipped with a heat sink for dissipating heat emitted from a heat source, and more particularly to a heat sink-equipped cooling apparatus suitable for use for cooling an electronic component such as a CPU or the like.
Heat generated or emitted from an electronic component such as a CPU or the like used in a computer is progressively increased with an increase in performance of the electronic component. Japanese Utility Model Publication No. 15982/1991 discloses a cooling apparatus which is so constructed that a cooling fan is arranged above a heat sink having a plurality of radiation fins radially arranged on a front surface of a base plate thereof, to thereby permit air discharged from the cooling fan to be fed to a central region of the base plate and then outwardly exhausted through the radiation fins. Another conventional cooling apparatus is disclosed in U.S. Pat. No. 5,629,834 (corresponding to Japanese Patent No. 2,765,801 and Japanese Patent Application Laid-Open Publication No. 111302/1985) and U.S. Pat. No. 5,782,292 (corresponding to Japanese Patent Application Laid-Open Publication No. 102566/1997, which includes a heat sink having a plurality of radiation fins arranged in directions of flowing of air radially discharged from an impeller of a fan. In the cooling apparatus disclosed, the radiation fins are arranged so as to surround a part of the impeller of the fan. A further conventional cooling apparatus is disclosed in U.S. Pat. No. 5,785,116 (corres. to Japanese Patent Application Laid-Open Publication No. 219478/1998), which includes a heat sink having a plurality of radiation fins arranged on a base plate thereof so as to surround an impeller of a fan. The radiation fins are arranged in a manner to be inclined with respect to a central line extending through a center of the fan. In the cooling apparatus thus constructed, the heat sink including the plural radiation fins is formed by subjecting a cylindrical material to cutting which is carried out in a direction inclined with respect to a central line of the cylindrical material. Also, in the cooling apparatus, predetermined accurate relationship must be established between an angle of the radiation fins and an angle of the blades of the fan in order to permit the cooling apparatus to exhibit satisfactory cooling performance. Further, a motor of the fan is mounted on the heat sink.
The first and second conventional cooling apparatus described above each are not suitable for use for cooling an electronic component increased in heat generation. The third conventional cooling apparatus described above is suitable for cooling an electronic component increased in heat generation as compared with the first and second cooling apparatus. However, in the third cooling apparatus, the heat sink is increased in manufacturing cost and it is required to increase machining accuracy. Also, the third apparatus, as described above, is so constructed that the radiation fins are arranged so as to surround the impeller of the fan. Such arrangement causes a size of the cooling apparatus in a radial direction thereof to be significantly increased. Further, mounting of the motor of the fan on the heart sink in the third apparatus causes transmission of heat from the heat sink to the motor, leading to a deterioration in durability of the motor.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, It is an object of the present invention to provide a heat sink-equipped cooling apparatus which is capable of exhibiting increased cooling performance and durability and reducing a size thereof in a radial direction thereof.
It is another object of the present invention to provide a heat sink-equipped cooling apparatus which is capable of being reduced in manufacturing cost thereof.
It is a further object of the present invention to provide a heat sink-equipped cooling apparatus which is capable of being simplified in manufacturing thereof.
It is still another object of the present invention to provide a heat sink-equipped cooling apparatus which is capable of permitting the number of radiation fins arranged to be increased to a degree sufficient to enhance cooling performance of the cooling apparatus.
It is a still further object of the present invention to provide a heat sink-equipped cooling apparatus which is capable of permitting mass production thereof.
In accordance with the present invention, a heat sink-equipped cooling apparatus is provided. The cooling apparatus includes a heat sink for dissipating heat generated from a heat source. The heat sink includes a base plate increased in thermal conductivity and including a front surface and a rear surface with which the heat source is contacted, a virtual central line defined so as to extend in a direction perpendicular to the front surface of the base plate, a plurality of virtual vertical planes defined so as to extend in both a radial direction from the central line and a vertical direction perpendicular to the front surface of the base plate and be spaced from each other at equal intervals in a circumferential direction of a virtual circle defined about the central line, and a radiation fin unit mounted on the front surface of the base plate in a manner to be heat-transferable and including a plurality of radiation fins arranged so as to surround the central line while aligning the central line with a center in arrangement of the radiation fins. The cooling apparatus also includes a cooling fan including an impeller which includes a plurality of blades and is rotated by a motor and mounted on the heat sink so that the impeller is positioned above the radiation fin unit.
In the heat sink, the radiation fins each include a lower edge positioned on a side of the base plate, an upper edge positioned opposite to the lower edge, and a radiation surface positioned between the lower edge and the upper edge. The radiation fins each are fixedly mounted directly or indirectly on the front surface of the base plate so as to be positioned on an intersection line between the virtual vertical plane corresponding to each of the lower edges and the front surface of the base plate. Also, the radiation fins each are arranged while being inclined in an identical direction with respect to the virtual vertical plane (or toward one side in the circumferential direction of the virtual circle) so that an inclination angle xcex8 of predetermined degrees between the radiation surface of the radiation fin and the virtual vertical plane may be defined. The radiation fin unit and cooling fan are arranged in positional relationship to each other which permits each of the blades of the cooling fan and the upper edge of each of the radiation fins to be opposite to each other. The cooling fan is arranged so as to permit cooling air to be fed to the radiation fins of the radiation fin unit. For this purpose, the cooling fan may be operated so as to blow air against the radiation fins. Alternatively, it may be operated so as to suck air from a side of the radiation fins.
When the impeller of the cooling fan and the heat sink are arranged in proximity to each other, air fed from the fan is substantially kept from being fed to a portion of the heat sink which is not opposite to the blades of the fan or a portion of the heat sink which is opposite to a cup member on which the blades of the impeller are fixed. Also, an air stream generated due to rotation of the impeller is not permitted to flow in an axial direction of the motor but is caused to flow in a direction of rotation of the impeller. Thus, arrangement of the radiation fins in a mere radial manner causes the radiation fins to act as flow resistance, to thereby fail to permit an increase in cooling performance of the cooling apparatus. This is also true of a structure which is constructed so as to forcibly flow air in a radial direction using an axial fan adapted to feed air in an axial direction, to thereby flow the air around radiation fins positioned outside an impeller, leading to cooling of the radiation fins. On the contrary, the structure of the present invention that air fed in the axial direction of the motor from the cooling fan is blown against the radiation fins from above the radiation fin unit enhances cooling performance of the cooling unit. Although this is not clearly supported by any specific theory, it would be considered that arrangement of the radiation fins employed in the present invention reduces flow resistance to air discharged from the cooling fan and produces a rapid air stream along the radiation surface of each of the radiation fins, to thereby increase the cooling performance. Thus, the cooling apparatus of the present invention exhibits cooling performance at substantially the same level as an expensive cooling apparatus conventionally used without being increased in dimensions in a radial direction thereof and ensuring satisfactory durability of the motor.
Ideally, the plural virtual vertical planes are defined so as to be spaced from each other at equal intervals in the circumferential direction of the virtual circle. This ensures substantially uniform cooling of each of the radiation fins and base plate, to thereby further enhance cooling efficiency of the cooling apparatus.
The radiation fin unit may be formed by subjecting a single metal plate increased in thermal conductivity to bending. This reduces a manufacturing cost of the cooling apparatus and facilitates manufacturing thereof.
In the present invention, the radiation fin unit may be constructed so as to attain both simplified manufacturing of the cooling apparatus and mass production thereof. More specifically, a single fan mounting metal plate joined to the front surface of the base plate is provided. The radiation fins each are formed of a flat metal plate. Also, the radiation fins each are fixed at the lower edge thereof on the fin mounting metal plate. The radiation fins may be mounted on the fin mounting metal plate in any suitable manner. For example, the radiation fins each are integrally mounted at the lower edge thereof with a flange for fixing. The flange is arranged so as to extend along a surface of the fin mounting metal plate and fixed on the surface of the fin mounting metal plate. The flange highly facilitates mounting of the radiation fins on the fin mounting metal plate.
The present invention may be constructed so as to further promote mass production of the cooling apparatus. For this purpose, the fin mounting metal plate is formed with a plurality of slits in a manner to radially extend from the central line and be spaced from each other at predetermined intervals in the circumferential direction. The radiation fins each are integrally formed at the lower edge thereof with a fit projection which is fitted in each of the slits. Also, the radiation fins each are joined to the fin mounting metal plate while keeping the fit projection fitted in each of the slits. This facilitates not only positioning of the radiation fins on the fin mounting metal plate, but joining of the radiation fins to the fin mounting metal plate while keeping the radiation fins inclined.
Alternatively, the base plate may be formed with a plurality of slits in a manner to radially extend from the central line and be spaced from each other at predetermined intervals in the circumferential direction. In this instance, the radiation fins each are integrally formed at the lower edge thereof with a fit projection which is fitted in each of the slits. Also, the radiation fins each are joined to the fin mounting metal plate while keeping the fit projection fitted in each of the slits. This reduces the number of parts required although it somewhat increases a manufacturing cost of the apparatus. Alternatively, the radiation fins each equipped with the fixing flange may be directly fixed on the front surface of the base plate.
The radiation fins may be formed into the same configuration. This leads to a reduction in manufacturing cost of the radiation fins and therefore the cooling apparatus. In order to cut out a number of radiation fins from a single large-sized metal plate by punching with increased yields, the radiation fins each preferably have a main portion formed into a substantially rectangular shape. Thus, the radiation fin unit is permitted to be provided at a central portion thereof with a space of a frust conical configuration while having a center positioned on a central line of the radiation fin unit and being gradually reduced in diameter toward the base plate.
The inclination angle xcex8 of the radiation fins is basically varied depending on the number of radiation fins. An increase in number of radiation fins leads to a reduction in inclination angle, whereas a decrease in the number leads to an increase in inclination angle. However, the inclination angle xcex8 is preferably less than 45 degrees. The inclination angle of 45 degrees or more leads to a reduction in number of the radiation fins, to thereby cause a deterioration in cooling performance of the radiation fins. More preferably, the inclination angle xcex8 is less than 45 degrees and more than 15 degrees, because it increases the number of radiation fins to a degree sufficient to ensure satisfactory cooling performance of the radiation fin unit.
The cooling fan is preferably constituted by a so-called axial fan. The blades of the cooling fan are preferably inclined in a direction identical with a direction in which the radiation fins are inclined. In this instance, the cooling fan may be operated to rotate the impeller in the direction in which the radiation fins are inclined. This enhances cooling performance of the cooling fan.